The present invention generally relates to waste management systems. More particularly, the present invention relates to such a system that utilizes a source of positive pressure for transferring waste at a high velocity. More specifically, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, one particular aspect of the present invention pertains to a waste transfer system having a hopper that is pressurized with a source of compressed air and includes a downstream valve that is opened to project waste from the hopper.
Vehicles including recreational vehicles (xe2x80x9cRVsxe2x80x9d), airplanes, boats, trains, and the like conventionally incorporate bathrooms and associated waste management systems for the convenience and comfort of the passengers. Waste from an associated toilet is normally stored in a holding tank. It is not always possible or desirable to place the holding tank directly under the toilet. Manufacturers of these vehicles desire to make them as xe2x80x9chomelikexe2x80x9d as possible. In addition to general comfort and aesthetic features, this means that the vehicle toilets should be able to flush all foreign objects typically accommodated by a residential toilet.
Various types of waste transfer systems have been developed over the years in an effort to advance the pertinent art. One common type of system relies on a negative pressure differential or vacuum to transfer waste to a holding tank. One example of a vacuum type waste transfer system is shown and described in U.S. Pat. No. 4,819,279. The system of U.S. Pat. No. 4,819,279 includes a single pump with valves on opposite sides that allow the pump to serve as a vacuum source and to discharge holding tank contents.
The limitations of vacuum differential type systems, such as the one disclosed in U.S. Pat. No. 4,819,279, are well known. For example, such systems are generally limited to a maximum theoretical differential equal to atmospheric pressure (14.7 PSI at sea level). In practice, the actual differential used is considerably less. In order to pull waste completely through the system, it is necessary to provide a costly vacuum reservoir towards the downstream end of the system. Due to weight and cost constraints, this vacuum tank is typically limited to about 5 PSI under atmospheric pressure. The problem of possible collapse is inherent in the flexible discharge lines and also limits the maximum available negative pressure to much less than the theoretical maximum. Finally, the cost of vacuum pumps increases as the amount of negative pressure increases.
In another known type of waste transfer system, flush water is pressurized to facilitate flushing. Such pressurization is referred to in the art as xe2x80x9cjet assistxe2x80x9d. In a standard, siphon-type toilet, jet assist has been conventionally used to impart some energy to water standing in the bowl and thus trigger the siphon effect with less water than would normally be needed. While perhaps beneficial for certain applications, this effect is of no use in vehicle systems that typically empty waste directly and do not rely on a siphon for flushing.
Conventional waste transfer systems have also incorporated cutting blades for waste maceration. Such maceration type systems typically utilize a two stage process with maceration by a rotary chopper followed by pumping of the macerated waste. One example of such a system is shown in U.S. Pat. No. 4,156,297.
Systems that rely on maceration are generally associated with two major deficiencies. The first deficiency is that known macerators do not reliably handle tough fibrous waste. The material gets caught in the macerator and eventually stops it, resulting in inconvenience and added expense for repair. These systems are similarly unable to accommodate hard objects such as pebbles and coins that frequently find their way into the system. The second major deficiency is that the pumps used to move liquid waste cannot pump air. Therefore, the only ways to completely clear the discharge lines is to either have a downwardly draining system or continue to introduce clean water into the line after the waste as entered it using an impractical amount of water.
A final type of system known in the art utilizes a positive airflow to assist waste transfer. One such system is shown and described in U.S. Pat. No. 3,720,962. In the system of U.S. Pat. No. 3,720,962, a positive air flow is used to assist the transfer of waste from a hopper and through the discharge lines. The flush cycle is 3 to 15 seconds, with 5 seconds considered to be optimal.
Conventional systems utilizing a positive pressure assist fail to complete clear the discharge lines without a downwardly draining systems. This inability to clear the discharge lines becomes more significant as the horizontal travel distance increases. When the discharge lines are not completely cleared, undesirable odors can permeate through them. This problem is specifically addressed in U.S. Pat. No. 6,216,284 which discloses costly discharge lines designed to eliminate odor permeation.
Known waste transfer systems have proven to be generally acceptable for their intended application. It will not be appreciated, however, that all systems are all associated with disadvantages. Some of these disadvantages are discussed above. Continuous advancement of the pertinent art is therefore desirable.
It is a primary object of the present invention to provide a waste transfer system that overcomes the limitations of the prior art, including but not limited to those limitations discussed above.
It is another object of the present invention to provide a waste transfer system for a motor vehicle that allows for improved flexibility in relative placement between a toilet and an associated holding tank design.
It is another object of the present invention to provide a waste transfer system able to quickly and efficiently transfer waste in a vertically upward direction and for long distances horizontally.
It is another object of the present invention to provide a waste transfer system with high tolerances to foreign objects.
It is another object of the present invention to provide a waste transfer system that is able to utilize smaller diameter, less costly discharge plumbing hoses and/or pipes which are inherently less costly and more flexible.
It is another object of the present invention to provide a waste transfer system in which waste water exists a hopper under high pressure and at high speed.
It is another object of the present invention to provide a waste transfer system in which discharge lines are substantially cleared of waste water.
It is another object of the present invention to provide a waste transfer system with improved reliability.
It is another object of the present invention to provide a waste transfer system which breaks up waste without the need of a mechanical macerator.
According to one aspect, the present invention provides a waste transfer system including a toilet bowl, a discharge pipe, and a hopper. The hopper is positioned between the toilet bowl and the discharge pipe. A first valve is disposed between the toilet bowl and the hopper. A second valve disposed between the hopper and the discharge pipe. A source of compressed air is in communication with the hopper for pressurizing the hopper to a predetermined pressure until release by the second valve.
In a related form, the present invention provides a waste transfer system including a toilet bowl, a discharge pipe, and a hopper. The waste transfer arrangement further includes a valving arrangement operative to permit the introduction of material from the toilet bowl to the hopper under the force of gravity, selectively seal the hopper, pressurize the hopper to a predetermined pressure with a source of compressed air, and discharge the material from the hopper to the discharge line by quickly depressurizing the hopper from the predetermined pressure to an atmospheric pressure.
According to another aspect, the present invention provides a method of transferring waste through a waste transfer system having a hopper positioned between a toilet bowl and a discharge pipe. The waste transfer system includes a first valve between the toilet bowl and the hopper and a second valve between the hopper and the discharge pipe. The method includes the step of opening the first valve to permit the passage of waste from the toilet bowl to the hopper and subsequently closing the first valve to seal the hopper. The method additionally includes the step of pressurizing the hopper while the first and second valves are closed. The method further includes the step of opening the second valve to thereby force the waste from the hopper into and through the discharge pipe. The hopper is preferably pressurized to a predetermined pressure of approximately 30 to 80 PSI and the method preferably includes the step of depressurizing the hopper from the predetermined pressure to atmospheric pressure in less than approximately one second.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.